The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus for recording an image on a continuous recording medium such as paper, a sheet type plastic film and the like.
Various kinds of image recording apparatus for recording an image on a continuous paper have been developed. For example, the image recording apparatus is provided with an image recording portion for actually performing printing on the continuos paper. As a printing mode in this image recording portion, an impact mode using a wire or a hammer and a non-impact mode represented by an electrophotographic mode are known.
As a method for feeding the continuous paper, there are two methods, i.e., a method using feed perforations and a frictional feed method using a roller. In the feed method using the feed perforations, a plurality of pins are fitted in the feed perforations formed on the continuous paper. These pins are provided on the belt surface of a tractor having a rotary driving portion. When the belt of the tractor is rotationally driven, the continuous paper is given a feeding force.
When the image recording portion performs image printing (development and transfer printing in practice) on the continuous paper to which the feed perforations are formed by the electrophotographic mode, the continuous paper is fed to a fixing part by the tractor. In the fixing part, the image on the continuous paper is stabilized by carrying out a fixing process.
In general, the fixing part is provided with a heating roller and a pressure roller at an inside thereof. The continuous paper is sandwiched between these rollers and drawn from an image recording portion to the inside of the fixing part. Thus, when the continuous paper is fed from the image recording portion to the fixing part by the tractor, disadvantages such as slack or cutoff of the continuous paper is resulted if a large difference in speed between the tractor and the both rollers in the fixing part occurs.
For example, JP-A-8-50382 discloses that tension is applied to the continuous paper to absorb the abovementioned difference in speed in order to prevent these problems from occurring. This publication discloses a plate which pivotally comes into contact with the entire area of the back surface of the continuous paper in order to apply the tension to the continuous paper. A pivot position of the plate is adjusted. Since only printing on one surface of the continuous paper is described in this prior art, an unfixed image is not distorted even if the plate is brought into contact with the entire area of the back surface opposed to the printed surface.
However, in this prior art, when trying to print on the both surfaces of the continuous paper, since the plate is brought into contact with the entire area of the back surface of the continuous paper, the unfixed image is distorted and a normal result cannot be obtained. Since the need for printing a multi-color image or a full-color image on both surfaces has been increased in recent years, the technique disclosed in this prior art is not sufficient. Further, in this prior art, the plate is simply brought into contact with the continuous paper, and therefore, there is also a problem that the continuous paper tends to be displaced in the width direction thereof.
Further, as another prior art, there is JP-A-5-310351. In this prior art, disclosed is a technique that a continuous paper is printed by a laser printer and then in an after processing device, the printed continuous paper is cut into sheets of a predetermined size to be stacked. In this case, a roller which floats on the continuous paper stretching between two fixed rollers is provide in order to absorb a difference between a feeding speed in the laser printer and a fetching speed in the after processing device, and the continuous paper is given a slack, thereby absorbing the difference in speed. Since the continuous paper has been already fed out from the laser printer, fixation of an image formed on the continuous paper is already completed. Typically, a tractor and a fixing part are provided in the inside of the laser printer. This prior art does not clearly disclose means for solving problems which may occur when there is a difference in speed between the tractor and the fixing part.